This document discusses electric current, conventional current, actual electron flow, and resistivity. It defines current as the flow of electric charges and explains that conventionally it is defined as flowing from the positive terminal of a battery to the negative terminal, whereas actually electrons flow from the negative to positive terminal. It provides the equation for current (I=Q/t) and defines resistivity as a material's ability to resist current flow. Resistivity depends on temperature, length, cross-sectional area, and is inversely proportional to conductivity. Ohm's law relating current, voltage and resistance is also summarized.

1. MODULE4:
Current, Resistivity, and Resistance

2. W h a t i s i t
Electricity is a kind of energy that takes in many forms,
and one of this is the current electricity or electric
current. Electric current refers to the interaction of
charges in motion from one region to another.

3. W h a t i s i t
Electric circuit, on the other hand, occur the moment
when the charges in motion within a conducting path
forms a closed loop.

4. W h a t i s i t
Current represents the flow of electrons, however it
flows from the positive terminal of the battery towards
the negative terminal, and it is the common way of
representing the flow of current in an electric circuit,
that is how it perceive, thus it is called conventional
current, the choice or preferred current flow, so the
moving charges are considered positive, so it is
assume that it is moving in the same direction with
current.

5. W h a t i s i t
On the other hand, the opposite direction is the actual
flow of electrons, from the negative terminal to the
positive terminal

6. Differenceof
C O N V E N T I O N A L C U R R E N T A N D
A C T U A L E L E C T R O N F L O W

7. WHATISIT
I=Q/t
where:
I= current in Ampere
Q=charge in coulomb
t = time in seconds
The electric current flows from the
circuit shows the flow of electricity.
Given the equation current can also
be described in terms of the rate of
charges flow over time. It represents
how many electrons per seconds are
flowing at any given point Ampere
(A), the SI unit of current is defined as
one coulomb per second (1 A=1 C/s).

8. W h a t i s i t
Example:
A current of 5 A flows through a resistor for 30 minutes.
How many electrons flows through the resistor during
the time given?

9. W h a t i s i t
There are other factor and properties that affects the flow of
electric charges, and one of which is voltage and resistance
aside from current. Its relationship is summarized and
explained by Ohm's Law, which named after George Simon
Ohm. It states that the current is directly proportional to
voltage and inversely proportional to resistance as shown in
the equation below.
I=V/R
where: V= Volts, I= Current, R= Resistance (in Ω)

10. W h a t i s i t
Conductivity is the ability of the material to mobilize
charges. It is the opposite of resistivity Moreover, resistivity
(p) is defined as the resistance offered by the material
directly proportional to the length of the conductor and
inversely to its cross-sectional area. The SI unit of resistivity
is Ohmmeter (Ω.m)

11. R e s i s t i v i t y a n d
T e m p e r a t u r e
The resistivity of a metallic conductor nearly always
increases with increasing temperature As temperature
increases, the ions of the conductor vibrate with greater
amplitude, making it more likely that a moving electron will
collide with an ion. This impedes the drift of electrons
through the conductor and hence reduces the current. Over
a small temperature range (up to 100°C), the resistivity of a
metal can be represented approximately by the equation

12. W h a t i s i t
Resistivity is the ability of the material to
resist the flow of the electric current or the
electric charges. The electrical resistivity of a
conductor material is measured by how
strong the material opposes the flow of an
electric current in a circuit path.

13. W h a t i s i t
Materials such as copper and aluminum are known
for their low levels of resistivity thus allowing
electrical current to easily flow through them
making these materials ideal for making electrical
wires and cables. Silver and gold have much low
resistivity values, but for obvious reasons are more
expensive to tum into electrical wires.

14. W h a t i s i t
The following are the factors that affect the
resistance (R) of a conductor in ohms.
• The resistivity (p) of the material from which
the conductor is made.
• The total length (L) of the conductor.
• The cross-sectional area (A) of the conductor
• The temperature of the conductor.

15. Calculate the total DC resistance of a 100meter roll
of 2.5mm² copper wire if the resistivity of copper at
20°C is 1.72 x 10-8 meter.
W h a t i s i t

16. W h a t i s i t
Resistance (R) is directly proportional to the length
of the conductor and inversely to Its cross-
sectional area. The SI Unit is 1 Ω which is also
equivalent to 1 Volt over 1 Ampere.

17. W h a t i s i t
Example:
A 20meter length of cable has a cross-sectional
area of 1mm² and a resistance of 5 ohms. Calculate
the conductivity of the cable.

18. Thanksforlistening!